Analytical instruments should be as versatile as possible to minimize the number of different analytical instruments required in a single location, such as at a hospital or laboratory. It is therefore desirable to have an analytical instrument that handles test tubes of various types and sizes and both open ("uncapped") and closed ("capped") test tubes. Where the instrument requires the test tubes to be open before they are pretreated, sampled and tested, the instrument should have an automatic decapper to automatically decap closed test tubes. (As used herein, open test tubes, which do not require decapping, include containers like Microtainer holders.RTM. and Ezee Nest.RTM. inserts.)
Automating the decapping of test tubes is complicated by the variety of available test tubes, which may vary in diameter, height, and especially the variety of available caps to cover the test tubes. Some caps unscrew from threading on the top of the test tubes. These include caps for test tube-specific caps manufactured by Sarstedt of Germany, Braun, also of Germany, Meditech, Inc. of Bel Air, Md., and Greiner, as well as HemaGuard.RTM. caps used on Vacutainer.RTM. test tubes from Becton Dickinson. Another type of cap is a rubber stopper inserted into a test tube, such as a Vacutainer.RTM. test tube, which is removed by a pulling motion. The caps may also differ in their composition--they may be rubber, plastic, etc. A single decapper that can decap all of these tubes is needed because it is impractical to provide separate decappers in a single instrument for each type of cap.
In decapping the tubes, care must be taken not to break the tubes, generally made from glass or plastic, and not to spill any of the sample. There is a further constraint that portions of the sample and vapors not be transmitted to other tubes in the instrument which would interfere with the testing and analysis of the samples.
Automatic decappers have not previously been designed to remove from test tubes both screw-on caps and caps that must be pulled out. Generally, decappers have only been designed to decap test tubes sold by the same manufacturer. In one such system, Becton-Dickinson Model 704999 illustrated in a recent catalog in Germany, it appears that only Vacutainer.RTM. test tubes with rubber stoppers may be decapped. In another automatic decapper manufactured by Sarstedt, only screw-on caps on Sarstedt test tubes may be automatically removed with Sarstedt's decapper. Yet another automatic decapper from Terumo of Japan only decaps VenoJect test tubes manufactured by Terumo, which have a foil cap that must be cut off with a knife edge.
SmithKline Beecham Corporation also manufactures an automatic decapper for decapping test tubes but this decapper, which is designed for use as a station along a laboratory automation transport line, only pulls rubber stopper caps upwards and off of test tubes that are held in a stationary position. This decapper is not well-suited to be incorporated into a reasonably-sized analytical instrument as it is relatively large.
It would therefore be advantageous to have a decapper incorporated into an analytical instrument to decap test tubes both when an instrument is operated independently or as a backup decapper where the instrument interfaces with a lab automation system, should a freestanding decapper stationed along the transport line malfunction. While the space occupied by current freestanding decappers for use with a lab automation transport line may be relatively large, the decapper incorporated into an analytical instrument must be relatively compact to keep the instrument to a reasonable size. It should also be removable from the instrument for easy cleaning.